1. Field of the Invention
The present invention relates generally to apparatus for adjustably mounting and positioning precision components, elements and devices. More particularly, the present invention relates to apparatus for positioning optical elements, such as optical fibers and waveguides, where the position of the optical element can be precisely adjusted relative to three linear axes and two rotational axes.
The use of adjustable mounting apparatus for supporting optical components, such as optical fibers, mirrors, beam splitters, lenses, gratings, and the like, is known. For example, it is frequently necessary to position a first optical element, such as an optical fiber or waveguide, relative to a second optical element, such as another optical fiber or waveguide, a microscope objective lens, or the like. Frequently, the relative positioning of such optical components must be very precise, with accuracies on the order of wavelength dimensions sometimes being necessary. In the future, it is expected that allowable tolerances will be even smaller.
In order to provide for multiple positional adjustments, many previous component mounting devices have placed a series of independently positional stages or platforms on a single base. Each stage or platform is then adjustable in a single dimension relative to the underlying stage or base, thus permitting adjustment in as many dimensions as desired. While generally workable, such devices are mechanically complex and cumbersome. Moreover, each linkage between a stage and an underlying stage or base introduces six potential degrees of error in positioning. Thus, as the stages are built up one over another, the sources of error are compounded. For example, a component comprised of four stages mounted over a base will have twenty-four degrees of freedom, thus greatly reducing the overall stability of the platform. The model 19601 optical fiber positioner available from Oriel, Long Beach, Calif. is exemplary of such systems having multiple independently positionable stage elements built in series over a common base.
Another problem in the construction of precision component mounting devices arises from cross-coupling between position adjustment mechanisms. Cross-coupling refers to the disturbance of one positional parameter (in one degree freedom) arising from the change in another positional parameter (in another degree freedom). For example, changing position along one linear axis may cause an optical element to change its rotational orientation or to change its position along another linear axis. Often such cross-coupling effects are very small, but they can be significant in high precision systems.
For these reasons, it would be desirable to provide component mounting devices having improved stability, reduced cross-coupling between individual positioning mechanisms, and reduced complexity. In particular, it would be desirable to provide a mounting apparatus for optical fibers and waveguides, where the tip of the fiber or waveguide may be positioned at a desired location, with the location then being adjustable in multiple degrees of freedom with very high precision and repeatability. The mounting device should further provide for both coarse and fine position adjustment in at least some of the degrees of freedom, and should preferably provide for simplified use and implementation. In particular, it would be desirable to provide an optical fiber mounting device which comprises a single frame member and single stage member, where the frame member may be mounted on a surface and the stage member is positioned by a plurality of independent actuators which are grounded through the frame member.
2. Description of the Background Art
A six-axis precision positioning system having six independent linear actuators (with ball or sphere ends) is described in IBM Technical Disclosure Bulletin, Vol. 28, No. 12, May 1986. U.S. Pat. No. 5,077,622, describes a device for positioning an optical fiber or other optical element relative to an incident beam using positionable lenses. Mechanical clutches for precision linear positioning are described in U.S. Pat. No. Re. 30,406. A lever arm drive for a tangent screw mechanism is described in Kittel, Precision Mechanics-Class Notes (1989 Copyright) at page 23. Oriel, Long Beach, Calif., sells devices for mounting optical fibers relative to other optical elements, such as microscope objective lenses. The devices provide three degrees of translational positioning and two degrees of rotational positioning with coarse/fine adjustment in the nominal vertical and horizontal directions. Model 19601 available from Oriel is exemplary of the coupling devices described above. Other optical fiber mounting devices are commercially available from various suppliers such as Newport, Fountain Valley, Calif. (Model 561); Melles Griot, Irvine, Calif. (Model 07HF001); and Ealing, Holliston, Mass. (Model 35-7426).
U.S. Pat. No. 5,140,470 commonly assigned with the present application, describes an optical mounting apparatus having a stage plate mounted on a backing plate with three axial actuators capable of providing axial translation and rotation about two transverse axes. Copending application Ser. No. 07/785,773, commonly assigned with the present application, describes a support platform which is positionable in four degrees of freedom through a single base.